a), b): J-maps derived from heliospheric imaging made by STEREO-A showing the state of the interplanetary medium between 16 April and 6 May 2008. Each track on these J-maps corresponds to a density structure moving radially outward from the Sun and leaving a strong signature in the white-light images. The horizontal dotted line near the top of the maps shows the elongation of STEREO-B (STB). The inclined red line in a) is the track of a hypothetical CME launched near the time of the 26 April 2008 event and propagating at constant speed 550 km s^-1. The vertical blue line marks its arrival at STB. c), d): view of the ecliptic plane from solar north with the respective locations of STEREO-A (STA), STB and L1 as well as other planets and probes that are not all labeled for clarity purposes. The angular extents of the J-maps shown in the left-hand columns are shown as red contour lines emanating from the STA. The locations of the CME (c) and CIR (d); blue band) derived by the J-map analysis are shown at 12:00 UT on 27 April 2008. These four panels were produced using the IRAP propagation tool (propagationtool.cdpp.eu).